I. Field of the Invention
This invention relates generally to a split frame clamshell machining lathe for cutting and finishing relatively large diameter pipes, and more particularly to adjustable locators for aligning the large diameter pipes in the clamshell lathe.
II. Discussion of the Prior Art
Split frame clamshell lathes of the type described herein are known in the art. U.S. Pat. Nos. 4,739,685; 4,939,964; 5,549,024; and 6,619,164 are illustrative of the technology involved. The teachings of these patents are hereby incorporated by reference. As described therein, a clamshell machining lathe generally comprises a first and a second semi-circular segment that are designed to be joined together to form an annular assembly for encircling a shaft or pipe to be machined. The assembly also generally includes a stationary ring, and a rotatable ring supported by bearings affixed to the stationary ring. The rotatable ring includes a spur gear on its outer peripheral surface and is journaled to the stationary ring for rotation about a concentrically disposed pipe or work piece. A motor is attached to the stationary assembly and includes a drive gear designed to mesh with the spur gear on the rotatable segment of the pipe lathe. A tool block for supporting a cutting tool is mounted to the rotatable segment and is designed such that a cutting tool is advanced in small incremental steps in a radial direction against the pipe to be machined upon each orbit of the ring gear about the work piece.
A problem has heretofore existed in the prior art when the diameter of the work piece does not exactly correspond with the diameter of the clamshell housing. If there are no locators mounted to the inner circumference of the stationary member of the clamshell lathe, then the cutting may be uneven. To solve this problem, standard locators were inserted into pockets machined into the housing of the stationary member. The standard locators were then axially adjusted manually to accommodate different sized work pieces and to precisely center the clamshell lathe on the work piece. This type of adjustment was somewhat uncontrolled and tended to be inaccurate. Placing the prior art locators in an ideal position both axially and radially is a time-consuming endeavor.
While the prior art locators prove marginally acceptable for clamshell lathes to be used with piping or shafts up to five feet in diameter, when a clamshell lathe is built to machine work pieces whose diameters may be ten feet or greater, it becomes increasingly difficult to set up the machine because of the overall weight thereof. While the standard, prior art locators can be used to effect radial positioning so that the clamshell lathe annulus is concentric with the work piece to be machined, axial positioning becomes increasingly difficult. In the past, a brute force approach has been used where workmen axially position the clamshell lathe on the work piece using a sledgehammer to beat the clamshell to a desired axial position.
It is the purpose of the present invention to simplify the alignment of the locators and therefore the clamshell lathe by providing an adjustable locator which can be adjusted in both the axial and the radial direction. It is a further object of this invention to reduce the setup time required for mounting a clamshell lathe in a pipe or shaft to be machined and to reduce the amount of physical work involved.